Crushed coral for hard water

[RachelT]

How often do I need to swap out the crushed coral in my baggie that I have in my filter? Water always tests hard no matter how much coral I use! I have two Sunset Honey Gouramis and shrimp in a 8.5 gallon tank. Thanks! 

[nabokovfan87]

Welcome to the forum!

In my tank I am testing my water basically before each WC to try to keep track of how things are fluctuating.  That being said, that's my metric for how often I'll have to swap mine out.  In the filter box itself it's going to need to be changed more frequently than if it was passively in the tank as a substrate medium. 

I am intrigued though, you said your water always tests hard?  What do you mean by that?  Crushed coral is to boost KH generally, and so it won't reduce GH (General Hardness) in any real way.

I don't know if you've seen this before but it might be helpful so I'll share it!

https://www.aquariumcoop.com/blogs/aquarium/ph-gh-kh

[Cbass]

Crushed coral raises KH (Carbonate Hardness) and GH (General Hardness), which is why your water is testing hard. I would be careful as you are likely also affecting pH. 

So there are a couple of vids on the AC site that can help. This one helped me a lot. It's long, but worth a watch. What are your current water parameters, especially pH, KH, and GH? Also, what are the parameters of your source water? 

[xXInkedPhoenixX]

I agree that it seems to raise GH some but I didn't find in my tank it raised it much more than 2 or 3 points. It does however keep my KH stable and unless and until that changes I wait to add or swap more.